How to use the 'MESH_OT_extrude_verts_indiv' parameter?
Use bmesh



Strongly recommend using bmesh instead of bpy.ops.mesh whenever you can.

Here is my understanding of the script needed.  Extrudes the individual selected vertices randomly a number of repeats.

The operators return dictionary has the newly created vertices and edges.

import bpy
import bmesh
from mathutils import Vector
from random import uniform

context = bpy.context
ob = context.edit_object # edit mode!
me = ob.data
bm = bmesh.from_edit_mesh(me)
verts = [v for v in bm.verts if v.select]
for repeats in range(5):
    ret = bmesh.ops.extrude_vert_indiv(bm,
            verts=verts)
    for v in ret["verts"]: 
        v.co += Vector([uniform(-1, 1) for a in "xyz"])
    verts = ret["verts"]

bmesh.update_edit_mesh(me)


If the idea is to extrude from the same vert  repeat times, then remove the line

verts = ret["verts"}